This invention relates to lactone-fused aromatic compounds and their preparation.
Lactone-fused aromatic compounds are useful in perfumes, cosmetics and as food additives.
One class of lactone-fused aromatic compounds are coumarins, which correspond to the formula ##STR1##
Coumarins are prepared by reacting a phenol with maleic, fumaric or acrylic acid. Also, they can be prepared by reacting salicylaldehydes with acetic anhydride or malonic acid. See Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 7, 198-203 (1979).
Another class of lactone-fused aromatic compounds are coumar-2-ones which correspond to the formula ##STR2##
Coumaran-2-ones can be prepared by the cyclization of o-hydroxyphenylacetic acids. See Elderfield, Heterocyclic Compounds, Vol 2, 3 (1951).
Lactones have been prepared from unsaturated alcohols. Falbe, Carbon Monoxide in Organic Synthesis, Springer-Verlag N.Y., 157-158 (1967), teaches that a mixture of 5- and 6-membered ring lactones can be prepared from unsaturated alcohols when contacted with carbon monoxide in the presence of a cobalt-carbonyl or rhodium chloride catalyst at about 250.degree. C. and about 300 atmosphere. The disclosed reaction can be described by the following equation: ##STR3## wherein A, A' and A" are hydrogen or alkyl. See also Matzuda, Bull. Chem. Soc. Jap., 41(8) 1876-83 (Eng.).
What is needed is a process for the preparation of lactone-fused aromatic compounds. What is further needed is a process wherein the amount of catalyst is relatively low and the yield of the lactone-fused aromatic compounds is high. It is desirable to prepare lactone-fused aromatic compounds without using acids such as maleic acid, fumaric acid, acrylic acid, malonic acid or o-hydroxyphenylacetic acid, or using salicylaldehyde.